Hi there, I'm also looking into study a degree with the Open University and I, too, am unsure of which subject to choose.
I have studied biology, chemistry, maths and languages so far and I have never experienced anything different. I am not sure whether to go for another degree in science again, or choose a degree in language studies, or even go for something totally different like business or design?
It can be really confusing, it's a hard decision to make especially that it's our second degree (I didn't graduate from my previous degree course though).
I don't think business ever dies out, it's always a safe option, especially if you're doing something like a business management degree. English peaking managers are required in a lot of countries, especially in places like China and nearby Asian countries I heard.
Another quick option for you (since you already have a degree) is to teach English abroad (TEFL). Some countries pay really well. You can do that while you decide on what you want to study later on maybe?